Understanding the equine cecum-colon ecosystem: current knowledge and future perspectives

Abstract

Having evolved as a grazing animal, a horse's digestive physiology is characterized by rapid gastric transit, a rapid but intense enzymatic digestion along the small intestine, and a long and intense microbial fermentation in the large intestine. The process of understanding and describing feed degradation mechanisms in the equine digestive system in general, and in the hindgut ecosystem in particular, is essential. Regardless of its importance for the nutritional status of the host, the significance of the cecum-colon ecosystem has not yet been fully understood, and few reports have focused deeply on the contribution of the hindgut microbial population to the nitrogen and energy requirements of the horse. Compared to ruminal activity, very little is known about hindgut ecosystem activity in the horse. Information concerning the metabolism of this microbial population and its requirements is lacking. The use of internal bacterial markers for quantifying microbial outflow in ruminants is widely reported. These techniques can be applied to cecum-colon microbial quantification, contributing to a better characterization of this ecosystem. It is likely wrong to believe that the optimization strategy in the hindgut is similar to what happens in the rumen -that is, to maximize microbial growth and, therefore, fermentation. If we consider the type of substrate that, in normal conditions, arrives in the hindgut, we can expect it to be nitrogen limiting, providing limited nitrogen-based substrates for microbial fermentation. In this review paper, we intend to gather existing information on the equine ecosystem and to provide future perspectives of research.Keywords: horse, cecum, colon, digestive strategy ImplicationsThe process of understanding and describing degradation mechanisms in the equine digestive ecosystem in general, and in the hindgut in particular, is essential to provide information for proper feeding practices to be implemented. Regardless of its importance for the nutritional status of the host, the significance of hindgut fermentation has not yet been fully understood, and few reports have focused deeply on the contribution of the hindgut microbial population to the nitrogen and energy requirements of the horse. In this review paper, we intend to gather existing information on the equine ecosystem and to provide future perspectives of research. IntroductionHorses are free-ranging herbivores of grassland environments adapted to eat large quantities of high fiber feeds (Janis, 1976;Bennett, 1980). Nowadays, with the increase of their use in sports and leisure, many horses are housed during long periods of time and fed daily on two or three meals of forages plus concentrate. The forage component of the diet is sometimes characterized by having low-tomedium energy concentration and variable levels of fiber and protein (Micol and Martin-Rosset, 1995). This pattern of feed supply is not as expected by the horse's phylogenetic adaptation to grassland environments (Janis, 1976). These management procedures have i...

Horse-meat for human consumption — Current research and future opportunities

“…The digesta passage rate through their stomach and small intestine is quite fast in comparison to other ruminants (Udén, Rounsaville, Wiggans, & Van Soest, 1982), reaching the hindgut fermentative compartments 3 h after feed consumption (Van Weyenberg, Sales, & Janssens, 2006). Fibrous feed portions are submitted to microbial fermentation in the cecum and colon (Santos, Rodrigues, Bessa, Ferreira, & Martin-Rosset, 2011) with extensive absorption of volatile FAs produced that can contribute to 60-70% of their energy supply (Vermorel & Martin-Rosset, 1997). Equine hindgut has also the ability for selective retention of coarse particles in the cecum, and fluids and small particles in the colon as previously reviewed by Santos et al (2011).…”

“…Fibrous feed portions are submitted to microbial fermentation in the cecum and colon (Santos, Rodrigues, Bessa, Ferreira, & Martin-Rosset, 2011) with extensive absorption of volatile FAs produced that can contribute to 60-70% of their energy supply (Vermorel & Martin-Rosset, 1997). Equine hindgut has also the ability for selective retention of coarse particles in the cecum, and fluids and small particles in the colon as previously reviewed by Santos et al (2011). As indicated before, in comparison to ruminants, horses have faster passage rates (Udén et al, 1982;Van Soest, 1994) and, therefore, greater feed intakes (Menard et al, 2002) but only mild digestive efficiencies (Munn, Streich, Hummel, & Clauss, 2008).…”

Zaldi-haragiaren ezaugarritzea: konposizio kimikoa eta gantz-azidoen profila

“…Abere hauek elikadura-portaera jarraikia dute eta beren digestio-sistemari esker, bazka kopuru handiak irensteko gai dira. Dietako lipidoak nagusiki entzima endogenoei esker digeritzen dituzte, eta digeritutako % 90-95 heste meharrean xurgatzen dute [5]. Beraz, GA gehienak mikroorganismoen hartzidura-gunera (itsua/kolona) iritsi aurreko atalean xurgatzen dira, eta ondorioz, biohidrogenazio-aktibitatea hausnarkarietan baino baxuagoa da.…”

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“…Neste órgão o alimento permanece retido de 2 a 6 horas (SANTOS et al, 2011a), sendo adaptado à recepção de pequenas quantidades de alimento várias vezes ao dia. Este segmento representa cerca de 8 a 10% do trato digestório total (CUNHA, 1991) e os processos digestivos ocorrem pela atividade simultânea de enzimas digestivas, micro-organismos e suco gástrico (MEYER, 1995).…”

“…O intestino delgado inicia-se no piloro e termina na junção com o ceco, é dividido em duodeno, jejuno e íleo e representa aproximadamente 1/3 do volume total do trato gastrointestinal, chegando a 25 m de comprimento, o que torna o trânsito digestivo bastante rápido, cerca de 30 cm/min (FRAPE, 2004;JULLIAND et al, 2008;SANTOS et al, 2011a).…”